Ordinary toothbrushes are chiefly designed for the purpose of cleansing the surfaces of the teeth and gums, the areas between adjoining teeth (the areas between adjoining teeth are hereinafter referred to as "interproximal areas") and the marginal areas between the teeth and the gums (the marginal areas are hereinafter referred to as the "periodontal areas"), and removing dental plaque in the interproximal areas and the periodontal areas. This performance is hereinafter referred to as "cleansing performance". Also, the brushing with a toothbrush provides a massaging effect against the gums. Massaging the gums is known to be remarkably effective in preventing periodontitis or gumboil. This massaging effect is also one of the objects of toothbrush devices. In order to improve the cleansing performance, various types of toothbrushes have heretofore been proposed.
One such example is disclosed in Japanese Utility Model Publication No. Sho 61-10495 in which a toothbrush has tapered bristles and non-tapered bristles alternately embedded. The tapered bristles cleanse the interproximal areas and/or the periodontal areas, while the non-tapered bristles cleanse the surfaces of the teeth and gums. However, this toothbrush does not take into consideration a massaging effect against the gums. Therefore, the cleansing performance and massaging effect were left incompatible.
Another Japanese Utility Model Publication No. Sho 63-31640 discloses a toothbrush in which non-tapered bristles having ball-like distal ends of different height are embedded such that the distal ends are steppingly arranged, so that the massaging effect will be enhanced. However, since this toothbrush has non-tapered bristles having ball-like distal ends, the distal end portions are difficult to flex. Moreover, it has room for improvement with respect to the removal of plaque and a massaging effect.
Another Japanese Laid-Open Utility Model Application No. Hei 5-15834 discloses a toothbrush having bristles which are all tapered. This toothbrush is not sufficient in stiffniess as a whole and its bristles tend to overly flex. Accordingly, in spite of its comfortableness in sense of feel, it has deficiencies in cleansing performance and massaging effect.
Furthermore, Japanese Laid-Open Patent Application No. Hei 7-284412 and U.S. Pat. No. 5,500,975 disclose a toothbrush in which two types of bristle end forms, one being of a ball-like shape and the other being of a tapered shape, are folded into two parts and embedded in bored holes respectively. This toothbrush has, indeed, the advantages that the ball-like end form of its bristles provides a good massaging effect to the gums and a good plaque scraping-off effect, and that the tapered end form provides a good plaque-removing effect from the periodontal pocket. However, in spite of those advantages, this toothbrush has the deficiencies that the bristles having the ball-like end form are more difficult to be flexed than the bristles having the tapered end form, and that the first-mentioned group of bristles having the ball-like end form are degraded in sense of feel and comfortableness. Moreover, this toothbrush is also not satisfactory with respect to long service life.
The inventors of the present invention have studied very hard in order to overcome the above-mentioned deficiencies and finally succeeded in the development of a toothbrush capable of overcoming those deficiencies. It is, therefore, an object of the invention to provide a toothbrush which is excellent in performance with respect to the cleansing of surfaces of the teeth and gums, the areas between adjoining teeth, and the marginal areas between the teeth and the gums, and excellent in performance with respect to the massaging of gums, is comfortable in sense of feel, and is satisfactory in providing a long service life.